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[Bug dynamic-link/18402] FPU use in application before main()
- From: "dave at sr71 dot net" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Tue, 12 May 2015 15:03:39 +0000
- Subject: [Bug dynamic-link/18402] FPU use in application before main()
- Auto-submitted: auto-generated
- References: <bug-18402-131 at http dot sourceware dot org/bugzilla/>
https://sourceware.org/bugzilla/show_bug.cgi?id=18402
--- Comment #4 from Dave Hansen <dave at sr71 dot net> ---
For a statically-linked app, things are a bit different. I set a breakpoint
*at* strlen and then waited to see the FPU get used. When strlen() was called,
the FPU was not in use, but I single-stepped and saw it get used on the next
instruction. So perhaps there are two separate issues here?
(gdb) r
Starting program: /root/hellodave
Breakpoint 2, 0x00000000004191f0 in strlen ()
# Note, no FPU use here
(gdb) stepi
0x00000000004191f5 in strlen ()
# FPU has been used
(gdb) bt
#0 0x00000000004191f5 in strlen ()
#1 0x00000000004073a6 in getenv ()
#2 0x000000000043793e in _dl_non_dynamic_init ()
#3 0x00000000004386f8 in __libc_init_first ()
#4 0x0000000000401222 in __libc_start_main ()
#5 0x0000000000400f77 in _start ()
(gdb) disassemble strlen
Dump of assembler code for function strlen:
=> 0x00000000004191f0 <+0>: pxor %xmm8,%xmm8
0x00000000004191f5 <+5>: pxor %xmm9,%xmm9
0x00000000004191fa <+10>: pxor %xmm10,%xmm10
0x00000000004191ff <+15>: pxor %xmm11,%xmm11
0x0000000000419204 <+20>: mov %rdi,%rax
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